Marul was the leader of the people of Latona and was introduced in the episode, 5.20 "The Sentinel".
Three hundred years ago, the people of Latona built a planetary defense system called the Sentinel. The people were protected by this device and were allowed to pursue their other interests in matters of the mind and spirit. Only once in Marul's lifetime, when he was a small boy, did the Sentinel have to be used to protect their planet from attack. The device whisked these attackers away to the place where the builders deemed appropriate. No one knew exactly where that place was, but it was most likely the afterlife.
Because the people pursued non-material interests, they regressed in their technological knowledge. They depended upon the old technology, but were not able to repair it if it were to break down. When a rogue cell of the NID visited Marul and asked to see the Sentinel, he declined because it was forbidden by their laws. Marul kept the laws religiously. The rogue team, led by Col. Sean Grieves, did not bother to ask permission and so they found the Sentinel and attempted to learn its secrets on their own.
During their two weeks with the device, Grieves' team, which included Lt. Kershaw, was discovered by the Caretaker of the Sentinel. In his surprise, Grieves killed him. He then had Kershaw rig the deadman switch that the Caretaker wore so that the flame that it controlled continued to burn, an indication that the Sentinel was available if needed. This flame was in Marul's office.
Two years after Marul's encounter with the rogue NID cell, the Goa'uld System Lord Svarog attacked his planet. The Sentinel did not work. Marul insisted that it would because he saw that the flame continued to burn. SG-1 was sent to the planet to help the Latonans evacuate or repair the Sentinel.
Marul was attacked by the Jaffa under Svarog's service. He refused to help them locate the Sentinel and said that he'd rather die than break one of their most sacred laws.
Fortunately, the Sentinel was brought back online when Grieves stood in the Caretaker's place to activate it. The attacking Jaffa and mothership were made to disappear, along with Grieves himself.
Most probably, Marul severed all relations with the people of Earth after these events.
--DeeKayP 18:16, 17 Oct 2004 (PDT)